(1) Field of the Invention
This invention relates to a detergent composition for contact lenses, in particular a detergent composition which is useful for removing proteinaceous depositions or retentions from contact lenses. This invention also relates to a method of removing such depositions and retentions from contact lenses.
(2) Description of the Prior Art
Among contact lenses, there are hard contact lenses composed primarily of methyl methacrylate, soft contact lenses comprising 2-hydroxy methacrylate, and N-vinyl pyrolidone or silicone contact lenses which are made by subjecting the surface of a hydrophobic material made from polysiloxane series to an electrical discharge in order to make its surface hydrophilic. Since, in particular, soft contact lenses and silicone contact lenses are flexible, good in oxygen permeability and since they can easily be fitted when these lenses are on the eyes, these lenses are widely used nowadays.
When such flexible contact lenses are worn for a long time, lipid, protein, mucin in tear and bacteria are deposited on the surface and into the mass thereof. Those depositions make the lenses opaque and also injure the eye.
Lipid deposited on the surface of a contact lens can be removed therefrom almost completely by detergents containing a surfactant as the main component and said detergents are generally used for this purpose. They do not, however, remove proteinaceous and mucinic depositions. In particular, boiling and sterilization of the contact lens further modifies the protein, causing it to coagulate so that the protein becomes strongly fixed to the lenses. As a result, the life of the lens is shortened.
There have been known detergents comprising protease and hydrosulfohydryl compound for cleaning contact lenses deposited with protein and mucin. These detergents are effective in cleaning such lenses but have a weak point in that a long time is required for cleaning. There have also been known detergents prepared by adding at least one compound selected from urea and guanidine hydrochloride salt to said detergents in order to shorten the cleaning time. However, such shortening effect is not altogether satisfactory.